Friday, November 4, 2011

Frickin' Fracking...

Our intense and escalating addiction to sweet, sweet hydrocarbons combined with our collective paranoia about dependency on foreign oil (damn you Canada!) has driven some pretty clever advances in the petroleum geosciences. Whether in terms of important scientific concepts (like chronostratigraphic approaches to understanding the rock record, or facies model approaches to understanding paleoenvironmental characteristics) or in terms of applied engineering (i.e., all the different ways we now have to acquire and understand subsurface data sets), the need to exploit more and more of the Earth's hydrocarbons have led us into heady intellectual territory.

Some of the schemes utilized to find and recover hydrocarbons from the subsurface are downright Strangelovian. While THE goofiest has to be the Wagnerian boondoggle of CO2 sequestration, a close second in terms of seeming craziness is fracking. Hydrofracking, or simply "fracking" if you're "hip" and "with-it", is the process by which humans enhance the connectivity of an existing oil or gas field. Briefly, let's say you've got an gas field sitting out in the middle of nowhere. You know there's hydrocarbons in them there interstitial pores, but your wells aren't producing at the rate or capacity that you had hoped. What you do then is what every red-blooded human has done since we knapped our first flint; you IMPROVE on nature! In this case, you pump a slurry of quartz and who-knows-what chemicals under high pressure into the reservoir in question. The high pressure fluids initiate and build-up a series of new fractures, while the quartz grains prop open the newly anthropogenic fractures, allowing your hydrocarbon fluids to flow more freely.

Fracking has been done for quite a while; commercial use of hydrofracture techniques began in 1949, although people were apparently sending water/nitroglycerine mixtures into wells to do the same thing as early as the 1860s. A pretty good historiography of hydrofracking techniques can be found here.

Despite this long-term history, Fracking has been in the news recently, on account of Oil Companies expanding interests in shale gas reservoirs. Shales, of course, are noted for their very poor porosity and permeability; fine-grained muds undergo some pretty impressive compaction in the subsurface, resulting in "tight" rock that really restricts the fluid flow paths. Since the universe is largely ruled by Irony, however, mudrocks and shales are also often extremely rich in organic material. Organics, when subjected to the right conditions, are what we pump out of the ground in the form of oil and gas. So, these mud-rich reservoirs are often very high in organic content, but actually REMOVING the fluids-of-interest from those sopping shales can be tricky! What nature fails to provide, human ingenuity must produce; thus, frack the shit out of some shales, and viola! You've got a productive field where once was only a tight, uneconomical subsurface lithosome.

However, some spoilsports don't seem to be willing to embrace the Inevitable March of Progress, and have voiced some concern regarding hydrofracking. One of the things that seems to have really caught a lot of people's attention is the supposed link between fracking and seismicity. People are worried that, by producing new fracture networks in the subsurface, hydrofracking might be causing earthquakes. The idea of human-induced seismicity is one of those sort of Doomsday type things that freak folks out, and there have been a number of reports and anecdotes from folks in and around fracking sites claiming that there has been a noticable increase is earthquakes. But is there any evidence for such a link?

A company in the UK, Cuadrilla Resources, recently published a report that does, for perhaps the first time, actually seem to support the idea that hydrofracking can be linked to seismic events. The company was in the Bowland Basin in Lancashire, trying to exploit a shale gas play through hydrofracking. Their press release can be found here, while the pertinent (and actually fairly interesting) technical report is available as well, titled "Geotechnical Study of Bowland Basin Seismicity".

Briefly, the company had been monitoring seismic activity during their fracking proceedures, generally through the use of down-hole geophones. In the past, these had recorded seismic events well below the "0" magnitude threshold that were apparently closely associated with active hydrofracking. However, there were some larger events, including a 2.3 Magnitude event and a 1.5 Magnitude event that the company believes are highly likely to have been caused by their fracking. Importantly, neither of these events had any sort of structural effect at the surface, and didn't actually cause any sort of damage.

What is interesting is the fact that the company's study has identified a few contingent geological factors that seem to have been part of the reason for the fracking-induced seismic activity. These include structurally complicated stratigraphies with locally variable dips as well as pre-existing faults in the succession, which interacted in a sort of "perfect storm" with the hydrofracking to induce slip and result in a series of small earthquakes, including the two "big" ones mentioned above (2.3 and 1.5). The companies conclusion is that, yes Virginia, fracking DID (most likely) cause these specific earthquakes, but a) they weren't that big and didn't do any damage to structures or the the surface and b) the seismic activity was a result of fracking AND the presence of pre-existing structure. The company points out that these local conditions imply that fracking induced seismicity can be the result of very specific conditions that have to be met. Regardless, the report advocates continued monitoring in this and other settings, which would allow us to better understand both the mechanisms and processes that produce fracking seismicity, as well as predict those conditions in other fields in the future.

It's a pretty interesting report, and freely available online, which is nice. And while it does show that fracking CAN cause seismicity, for the reasons stated above it also shows that this seismicity is not that big a deal and actually probably really rare. And, to be honest, I never really FELT like there was much danger of fracking being a big deal in terms of causing earthquakes or destroying towns. Still, it's nice to have some actually science on the subject.

Of course, the REAL worry regarding fracking doesn't have anything to with earthquakes, in my opinion. That's just the sort of sexy catastrophe-mongering peddled by the popular press, and, at the risk of sounding conspiratorial, just the sort of low-risk/high-publicity kind of thing big Industrial/Business concerns like people worrying about. As Pynchon wrote in Gravity's Rainbow, "if they can get you asking the wrong questions, they don't have to worry about the answers".

The Earthquake worry is the wrong question to ask about fracking; what should be eliciting some raised eyebrows is the fact that companies are pumping huge volumes of unknown, proprietary fluids into the ground, with the expressed purpose of making it easier for fluids of ALL kinds to move more easily in the subsurface. Don't worry about earthquakes destroying central Pennsylvania; worry about ground water contamination! And not just from the mystery fluids used in fracking. There's all sorts of unpleasant things in the brines that lurk in the subsurface. I'd like to see a little more transperancy, and a LOT more science, on the question of what impacts, if any, fracking is actually having on groundwater and the environment.

And, as pointed out by the Cuadrilla report, it's often a question of local contingencies that matter. What might be perfectly safe in upstate New York COULD be disastrous in North Dakota, or in Wyoming, or in Romania. The question of fracking needs some serious study, particularly in light of the complicated natural systems that we geologists know characterize the actual Earth.

10 comments:

You're in luck! I ran across this article a while ago stating the U.S. Environmental Protection Agency's plans to conduct detailed case studies on the effects of "fracking" at seven different sites is multiple states: http://fuelfix.com/blog/2011/06/23/epa-selects-regions-for-fracking-studies-including-haynesville-and-barnett/

According to the U.S. EPA website, preliminary results will be available by the end of 2012, with the final report completed in 2014.

I'm pretty sure I saw something about the Dept. of Natural Resources doing something similar, but can't find any info on this (maybe it was one of the state DNR offices).

Either way, we should have at least one good set of data within the next two years.

Any critique of fracking needs to come after learning how the process actually works and what it takes to get a frac off in the first place. The most difficult thing to get an artificial frac to do is to grow up and/or down. Heterogeneity in mechanical properties between formations absorb and attenuate the vertical growth of an artificial fracture, and most fractures are limited to 10's of feet vertically from the perforations in the well casing that the frac is being pumped through. Given that most shale formations that are being fracked are at depths that are 1000's of feet below any aquifer, it is difficult to see how the water in the aquifer can be contaminated by fracking fluids that might move upwards 100 feet from the zone being fracked. A good analogy would be to slide a drinking straw in under a layer cake that's, say, 5 inches thick. Put a cc of water with food coloring in it into the straw and blow on it enough to "inject" the colored water into the cake around the opening of the straw. Then try to find a trace of the food coloring in the icing on the upper surface of the cake. Granted deep-seated faults that extend up to the aquifers could transport those fluids up, but that needs to be addressed on a case-by-case basis, not with a global condemnation of fracking.

@Craig Hall - I agree that discussions of fracking and public saftey/health need to be undertaken with some sort of knowledge base; my point in the post was that, despite the long history of hydrofracking, there really ISN'T much in the way of public, peer-reviewed science out there available for the public to ingest. Companies need to stop being so damn sanguine about the whole process, and look at fracking honestly and openly. As Nate pointed out in his comment above, the EPA is going to FINALLY start producing some data. That's great, but it's sort of silly that its been 15 or 20 years since the big frack-push began and we're just KNOW getting to that point.

Also, I think your cake analogy is a little misleading. We're not just putting ONE well down into a reservoit; we're putting lots and lots and lots of wells. And on each of those individual wells, we're not just doing ONE frack shot; a company is going to want to extend a fracture network along the length of a horizontal well leg. With each frack, and with each well, we start to hugely increase the probability that we're going to intersect a fault, not to mention produce hundreds of millions of liters of contaminated waste water that are going to cycle back up the well and have to be contained and treated.

If people are serious about safety and the environment, then we need more good science on the subject, including detailed seismic and geological surveys of the proposed area BEFORE fracking is done AND a carefully constructed plan for waste water remediation and monitoring afterwards.

Oh, and it would also be nice if fracking would fall BACK under the Safe Water Drinking Act, which it hasn't been subject to since 2005.

Excellent post. I agree, the anti-industry activists should stop trying to link every onshore earthquake to fracking just because of this one study. For example, people are trying to claim the Virginia EQ earlier this year is from Marcellus fracking -- problem is the EQ epicenter isn't in the Marcellus. People need to do a a bit of basic research (e.g., how about a map?) before making these claims.

And I wholeheartedly agree that industry needs to stop with the whole 'trust us' routine and participate in publicly available research about this issue. Open up if there's no issue.

Eric, I may be biased, but this is a really excellent post. I hope you don't mind me sharing it widely. Your point about asking the right questions is well made. We need to be scientifically informed *and* skeptical. Focusing on dubious earthquake claims is picking the wrong battle.

As if to confirm your main point, an article published by ProPublica notes that EPA has found some serious chemical contamination in Wyoming groundwater that is directly linked to fracking... even before the results of the bigger study are in.http://www.propublica.org/article/epa-finds-fracking-compound-in-wyoming-aquifer

Of course the article does a fair amount of scare mongering relating to the cancer causing potential of the discovered chemicals.... but it is an interesting article none-the-less

Probably (hopefully) an isolated incident...but one of concern none-the-less.

Here's an article re: the findings of a U of Texas study in which they found no direct link. However, there may be some indirect sources involved with the process. Not sure that this should be considered any better...

Very nice post. I would love to see more studies available about the geologic impact of fracking.

I know I'm late to the comment-party, but I would add the following:

First, there are very few studies regarding the fluids being injected because folks are still trying to figure out which fluids work best to propagate a fracture in a given medium. This is a huge issue in production engineering circles with groups who go to battle about gels vs. water-based vs. synthetic vs. oil-based vs.... you get the idea. So, over a couple square miles (and FYI, the well spacing in the Barnett Shale right now is << 40 acres; that's A LOT of wells real close together), you might have a whole variety of fluids being pumped down. Not only do we not know exactly what is mixing with rock and groundwater... we also don't know what might be mixing with each other. Creepy.

Second, I would say that the most difficult thing to get an artifical frac to do is not "to grow up or down". I would argue that it is predicting the growth. The major players in shale assets are doing their best to build and modify models to predict where fractures will go. When I worked the Barnett many moons ago, plenty of wells fracked down into the Ellenburger Formation, which is a water-filled unit. In some cases it was a fault. In others... a mystery. You get paid to produce gas though, not water, so it was always a priority to try to figure it out. Don't assume that only big faults will suck up fractures. Any weakness is a weakness.

Third, microseismic is a great piece of the puzzle. To get at that pesky 'where are my fractures going?' issue, a whole bunch of companies use downhole microseismic and create fracture maps. These maps show that: Fractures grow up. Fractures grow down. Fractures grow sideways. Fractures sometimes go where you hope they will go. Fractures sometimes go where you really hope they won't go.

So, I would encourage the industry: Publish those fracture maps. Publish that frac fluid chemisty. Be transparent and your models will undoubtedly get better.